This invention relates to testing apparatus for dynamoelectric machines, and in particular, to a test system and method for automatically performing a plurality of tests on a series of motors so that all motors in a series are tested.
It has long been the practice in the manufacture of dynamoelectric machines, and in particular, of electric motors, to run a series of operational and quality control checks to ensure that products produced by a motor plant, for example, are operating properly prior to shipment to a particular customer. Among the more common production tests imposed on motors during manufacture are a surge test of stator windings in which a high voltage surge is applied to the stator windings to check for wire damage that can result in an open circuit of the motor winding; a high pot or high potential test to check the motor windings for electrical shorts between windings and ground; and various start and run tests to ensure that the motor is operational.
With the growing concern over energy efficiency and zero-defect manufacturing, motor manufacturers more recently have been required to ensure that their motors meet other standards prior to shipment. For example, in addition to the above tests, the resistance of the motor's ground pin, the resistance of main and auxiliary windings, the static and dynamic balance of the motor, the free and locked rotor amps, along with other motor parameters are now often tested.
The direction of rotation of a motor also requires verification in many instances Again, with production volumes, it has heretofore been difficult to consistently check motor rotation, the historic test being a visual observation of the direction of rotation. In some instances a visual inspection may be difficult, and in any case such an inspection is prone to error and takes too much time.
Many of these concerns have been addressed in U.S. Pat. No. 4,383,439 to MacCormack et al. which discloses an automatic motor test board.
Even the MacCormack et al apparatus could be improved however. For example, additional tests are often required other than those performed by the MacCormack et al apparatus. Moreover, with the apparatus of MacCormack et al the testing process is fairly lengthy, which makes it disadvantageous to test all motors in a particular production run in a reasonable time and at a reasonable cost.
A further complication in motor testing is that the parameters of the motor vary with temperature of the motor, which often requires that all the testing be completed before the temperature of the motor changes appreciably.
Other motor defects are not easily detected by conventional systems even though they are often apparent to a human observer. Such defects are evidenced by a peculiar sound during motor operation. Such a sound is readily identified by a human observer, but has heretofore been undetectable by automated test equipment. Of course, using such a human observer increases the cost and time of the testing while increasing the opportunity for error.